Pain is a serious and sometimes debilitating problem. It is a symptom of many medical conditions, and can interfere with a person's quality of life and general functioning, and is the most common reason for physician consultation in most developed countries. Pain is the primary reason for more than 50% of emergency room visits, and is present in 30% of family practice visits. Pain may be either acute or chronic, persisting for minutes, such as during childbirth labor, or years, such as with rheumatoid arthritis, peripheral neuropathy, cancer, and idiopathic pain. Chronic pain is prevalent in 12-80% of the population, depending on the criteria used.
Pain is often localized to a particular region, possibly due to damage to tissue, stress, or overwork. One non-limiting example is injury to a muscle in the body, possibly due to strain or trauma. It is well known in the literature that specific locations in the body communicate pain to the brain through at least one spinal nerve. 31 pairs of spinal nerves exist in the body, with each one connecting to the spine via its nerve root. Mapping has been performed and published, which allows one to determine the spinal nerve or spinal nerves that communicate with a specific region of the body. One non-limiting example is cervical spinal nerves C5 and C6, which pass pain signals from the deltoid muscle of the shoulder to the brain.
Pain is generally managed with medications such as analgesics and anesthetics. Simple pain medications are useful in 20-70% of cases. Opioid pain relievers, such as codeine, meperidine, and oxycodone, are highly prevalent, with 207 million prescriptions written in the U.S. in 2013; however, pain medication often comes with significant side effects, which may include, but are not limited to, respiratory depression, constipation, dizziness, lightheadedness, feeling faint, drowsiness, nausea, vomiting, and addiction.
Many pain relievers are highly addictive when taken for extended periods, and the body tends to develop a tolerance to the medication, whereby a larger and larger dosage is required over time to achieve the same effect. It is apparent that a non-invasive, drug-free method for providing improved pain relief would be incredibly useful and desired.
Repetitive magnetic stimulation (rMS) uses a magnetic field generator that is placed near a target location and generates a series of magnetic field pulses roughly the strength of an MRI scan. One common use of rMS is transcranial stimulation to reduce the symptoms of a mental disorder, referred to as repetitive transcranial magnetic stimulation (rTMS).